1. Field of the Invention
The invention is concerned with a unitary seal formed of two distinct materials having different properties, said materials being directly bonded together without the use of an adhesive between them. Thus, an elastomeric sealing section can be made for such a seal backed by a support section of a high modulus, i.e., rigid, plastic. Such seals are tough and provide significant advantages for use in rough environments such as, for example, about shafts such as exist in loader linkage pin joints and the like.
2. Prior Art
Lip seals are, of course, quite well known to the prior art. Further, such seals have been made, as shown for example in U.S. Pat. Nos. 3,709,507 and 3,919,448, with backing members to provide support therefor. Such seals are discussed in even greater detail in an article entitled Dual-Material Molding of Radial Lip-Type Oil Seals by K. C. Rusch, R. W. Sanderson and H. VanOene published by the Ford Motor Company in the fall of 1970. It is further known, as discussed for example in U.S. Pat. No. 3,167,323, to make seals of polyurethane. Seals made of two plastic materials are further known, as shown for example in U.S. Pat. Nos. 3,765,690 and 3,771,801.
While the use of composite seals per se is old in the art, the use of such seals has presented a number of problems. First, the seals are not of unitary construction and the parts thereof can be dislodged relative to one another. This is, of course, extremely serious in heavy work environments wherein such seals are often subjected to very large forces. And, the simple gluing or adhering of a support member to a sealing member of such a seal would not adequately solve such a problem because the adhesive used might not be strong enough, formation of the composite dual material seal would require careful positioning of the parts together to avoid misalignment or the adhesive might not be completely uniformly spread between the two parts of the seal whereby leakage could occur in the non-adhered portion of the seal.
The present invention provides a unitary seal wherein the support and sealing sections thereof are directly bonded together without the use of an adhesive. This leads to a unitary seal of great toughness which can be used in rough environments such as on earth-working machines, for example, on loader linkage pin joints and the like. Further, the seal of the present invention can be formed by the methods of mass production, as described herein, thus removing the possibility of human error leading to misalignment of the support and sealing sections thereof.